WO2011/062191A, which will be hereinafter referred to as Reference 1, discloses a vehicle drive device including a clutch device that is arranged between an output shaft of an engine and an input shaft of a transmission for selectively connecting and disconnecting the output shaft and the input shaft to each other. The vehicle drive device disclosed in Reference 1 is switchable between a connected state in which the clutch device is engaged to transmit a driving force of the engine to the transmission and a disconnected state in which the engagement of the clutch device is released to interrupt the transmission of the driving force to the transmission. In the connected state, a piston member of the clutch device moves by a biasing force of an engagement spring to thereby bring a driving plate provided to face the output shaft of the engine and a driven plate provided to face the input shaft of the transmission in pressure contact with each other so that the driving plate and the driven plate engage with each other. In the disconnected state, an appropriate oil pressure is generated at a pressurized chamber by an operation of an electric hydraulic pump. Because of the aforementioned oil pressure, the piston member constituting the pressurized chamber moves against the biasing force of the engagement spring to release the engagement of the clutch device. In a case where the vehicle drive device is again shifted to the connected state, the pressurized chamber is disconnected from the electric hydraulic pump and is then connected to a reservoir. Then, an appropriate volume of hydraulic oil is supplied to a canceller chamber by the operation of the electric hydraulic pump so that a centrifugal oil pressure generated by oil that remains in the pressurized chamber is cancelled by a centrifugal oil pressure generated by the hydraulic oil at the canceller chamber. Consequently, the driving plate and the driven plate appropriately engage with each other by the biasing force of the engagement spring. In addition, in a case where the hydraulic oil is supplied to the pressurized chamber and the canceller chamber, the hydraulic oil partially diverges from an oil passage to be supplied to portions of the clutch device at which lubrication is necessary, for example, supplied to the driving plate, the driven plate, and a bearing portion.
According to the clutch device disclosed in Reference 1, for example, the hydraulic oil is supplied to the pressurized chamber and the canceller chamber by the electric hydraulic pump in required volume when necessary, thereby achieving a downsizing of the electric hydraulic pump. Nevertheless, the electric hydraulic pump that is downsized may have difficulty supplying a sufficient volume of lubricant simultaneously to the portions at which lubrication is necessary. In order to obtain a necessary volume of lubricant, the electric hydraulic pump may be enlarged.
A need thus exists for a clutch control system of a clutch apparatus for a hybrid vehicle which is not susceptible to the drawback mentioned above.